' THE ORIGIN OF SPECIES' 10; 



the fossil mammals from the Australian caves are nearly 

 allied to the modern kangaroos, phalangers, and wom- 

 bats; and the gigantic extinct sloths and armadillos 

 of South America are reproduced in their smaller repre- 

 sentatives at the present day. So, too, the moa of 

 New Zealand was a huge apteryx ; and the birds dis- 

 entombed from the bone-caves of Brazil show close 

 affinities to the toucans and jacanars that still scream 

 and flit in countless flocks among Brazilian forests. 

 The obvious implication is that the animals now in- 

 habiting any given area are the modified descendants 

 of those that formerly inhabited it. ' On the theory 

 of descent with modification, the great law of the suc- 

 cession of the same types within the same areas is at 

 once explained.' 



This last consideration leads us up to the argument 

 from Geographical Distribution. In considering the 

 various local faunas and floras on the face of the globe, 

 no point strikes one more forcibly than the fact that 

 neither their similarities nor their dissimilarities can be 

 accounted for by climate or physical conditions. The 

 animals of South Africa do not in the least resemble 

 the animals of the corresponding belt of South America; 

 the Australian beasts and birds and trees are utterly 

 unlike those of France and Germany; the fishes and 

 crustaceans of the Pacific at Panama are widely different 

 from those of the Caribbean at the same point, sepa- 

 rated from them only by the narrow belt of intervening 

 isthmus. On the other hand, within the same con- 

 tinuous areas of sea or land, however great the differ- 

 ences of physical conditions, we find everywhere closely 

 related types in possession of the most distinct and 



